Sir Alex Ferguson, one of the most successful football managers of all time, has made the "bombshell" announcement that he is to retire.

The 71-year-old said it was the "right time" to go after 26 years in which he has taken Manchester United to the pinnacle of the English and European game.

Sir Alex put an end to a flurry of rumours in a statement issued through United's website, saying: "The decision to retire is one that I have thought a great deal about and one that I have not taken lightly."

"I must pay tribute to my family, their love and support has been essential. My wife Cathy has been the key figure throughout my career," he added.

Everton boss and Sir Alex's fellow Glaswegian David Moyes has emerged as the frontrunner for the job and an appointment is expected by the end of this week. Senior sources confirmed that Real Madrid manager Jose Mourinho, who had been touted as the other leading contender, is not a candidate for the position.

Sir Alex will not leave United altogether when he bows out after the last game of the season against West Bromwich Albion on May 19 and will become a director and ambassador for the club.

Former Manchester United goalkeeper Peter Schmeichel described the decision as a "bombshell" and said that he "can't make sense of the timing".

Aside from current and former players, politicians, celebrity supporters and fans across the globe all paid homage to Sir Alex's glittering career.

David Cameron, who supports Aston Villa, tweeted: "Sir Alex Ferguson's achievement at #MUFC has been exceptional. Hopefully his retirement will make life a little easier for my team #AVFC". Labour leader Ed Miliband told reporters at Westminster the United manager had taught the "importance of teamwork, of dedication and commitment".

Star golfer Rory McIlroy and Simply Red frontman Mick Hucknall, both known for their love of the Red Devils, described Sir Alex's decision as "the end of an era", while BBC political editor Nick Robinson described him as the "greatest-living Briton".